ipv6 connexion fail - ipv4 OK

[Daniel <tech@tootai.net>]

Hi list,

I setup wireguard on a server running Debian 11 and get it to work with 
2 clients (Debian 11 and Ubuntu 20.04). Clients and server are on 
separate networks, one client behind a FW the other direct on Internet, 
no FW at all (VPS).

With this setup and ipv4 connection to the public IP of the server, 
everything is working as expected, ipv4 as well as ipv6 are passing 
smoothly.

Now I want to connect using the ipv6 address of the wg interface as both 
clients and server have ULA ipv6. This fail, wg show that connection is 
established but VPN is not usable. It's not a FW problem as I can ssh to 
the ipv6 address, as well as a netcat test from/to server IP -from each 
client- on an UDP port is working properly. Also, 
net.ipv6.conf.all.forwarding=1 is activated in sysctl.conf

All network stuff is done in /etc/network/interfaces which call the 
config file. The ipv6 address of the server is affected _to the 
wireguard interface_ (in ipv4 it's another interface who take care of 
the public address)

Server version is wireguard-tools v1.0.20210223.

If someone have any hint, thanks to share ;)
-- 
Daniel